Flame retardant compositions

ABSTRACT

A novel flame retardant composition is provided wherein the major component is a triphosphate ester of the formula: ##STR1## wherein R represents an alkylene radical of from 2 to about 10 carbon atoms and the halosubstituted derivatives thereof, R&#39; represents an alkylene radical of from 2 to 3 carbon atoms, X represents a halogen of chlorine or bromine, and n is an integer of from 1 to 5. In the preferred composition, R is ethylene or propylene and R&#39; is ethylene, X is chlorine and n is 1. The compositions are less fugitive than the prior art diphosphate compositions yet easier to prepare than low volatility phosphates presently manufactured by polycondensation.

This is a division of application Ser. No. 049,999 filed June 18, 1979and now U.S. Pat. No. 4,242,288, issued Dec. 30, 1980.

The present invention relates to a new group of halogenated triphosphateester compositions and their use as flame retardants.

PRIOR ART

Phosphorus flame retardant additives are well known as a class ofmaterials. To be an effective flame retardant additive, the compositionmust be economical to use, compatible and non-fugitive. The term"fugitive" is used to describe a composition whose flame retardingeffectiveness diminishes with aging, usually by volatilizing from thesubstrate. As an example, tris (2-chloroethyl) phosphate is a well knownflame retardant for flexible urethane foam. This material is initiallyeffective as a flame retardant when formulated as part of the foamforming reaction mixture. However, when the foam is subjected to aging,the flame retardancy of the foam is considerably reduced. For instance,the flame retardant volatizes from automobile upholstery material andfoam and contributes to the film formed on the inside of automobilewindows.

In an attempt to reduce the fugitive nature of the flame retardents,haloalkyl phosphate esters have been reacted with ethylene glycol toproduce a longer chain molecule. This is disclosed in Turley U.S. Pat.Nos. 3,707,586 and 3,817,881 which disclose forming a diphosphate esterof the formula: ##STR2## wherein R' is an alkylene radical of 1 to 8carbon atoms and R is a haloalkyl radical.

Similar compounds are disclosed in Birum U.S. Pat. No. 3,192,242 whichdiscloses the compounds: ##STR3## wherein R is haloalkyl and X ishalogen.

A further improvement over that obtained in U.S. Pat. No. 3,707,586 isdisclosed for the compounds in U.S. Pat. No. 3,976,619. Diphosphateflame retardants of the formula: ##STR4## wherein R and R' representalkylene radicals and n is 0 to 5 are prepared by reacting 2 moles ofphosphorus oxyhalide with one mole of a glycol or glycol ether. Thisintermediate reaction product is then reacted with an oxirane compoundto provide the desired diphosphate ester. The compositions of thepresent invention are not disclosed.

As an alternative attempt to prepare tris (2-chloroethyl) phosphateflame retardants which are less fugitive, Weil U.S. Pat. No. 3,896,187discloses polycondensing tris (2-haloethyl) phosphate until from 0.5 to0.9 moles of ethylene dihalide per mole of tris (2-haloethyl) phosphateare evolved. Mixed oligomers of the general formula:

    (ClCH.sub.2 CH.sub.2 O).sub.2 P(O)--OCH.sub.2 CH.sub.2 OP(O) (OCH.sub.3 CH.sub.2 Cl)].sub.n OCH.sub.2 Cl.sub.2 Cl

where the average n is greater than 1 are obtained. However, suchpolyphosphates have two faults:

(1) they contain labile cyclic impurities which require multiprocesssteps to remove them as disclosed in U.S. Pat. Nos. 3,891,727;3,959,414; 3,959,415; and 3,965,217; and

(2) the process for the preparation of the original oligomer results inthe formation of a toxic and wasteful organohalogen by-product.

The present invention is directed to the preparation of new flameretardant compositions with low volatility which are not required to beprepared by a polycondensation process as described above.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a novelflame retardant composition wherein the major component is atriphosphate ester of the formula: ##STR5## wherein R represents analkylene radical of from 2 to about 10 carbon atoms and thehalosubstituted derivatives thereof, R' represents an alkylene radicalof from 2 to 3 carbon atoms, X represents a halogen of chlorine orbromine, and n is an integer of from 1 to 5. In the preferredcomposition R is ethylene or propylene and R' is ethylene, X is chlorineand n is 1. The invention provides compositions which are less fugitivethan the prior art diphosphate compositions yet easier to prepare thanthe lower volatility phosphates presently manufactured bypolycondensation while avoiding the multiple processing steps requiredto remove labile cyclic impurities inherent in the polycondensationproducts without forming wasteful organohoalogen by-products.

DETAILED DESCRIPTION OF THE INVENTION

The products of the invention are prepared by reacting about 3 moles ofphosphorus oxyhalide with about 2 moles of polyalkylene glycol followedby reacting that intermediate reaction product with an oxirane compound.

The polyalkylene glycol used in the present invention can be representedby the formula:

    HO(R'O).sub.n R'OH

wherein R' and n are as described above. Preferably, R' represents analkylene group of 2 carbon atoms. The symbol n is preferably 1.Illustrative of the polyalkylene glycols which can be used in thepresent invention are diethylene glycol, triethylene glycol, dipropyleneas well as polyethylene and polypropylene glycols having repeatingglycol units of five or less. Included in the term dipropylene andpolypropylene glycol are all the isomeric forms thereof including thecommercially available mixtures of these isomers. It is intended thatthe compounds of the present invention also include mixed glycol etherspecies prepared by using two different polyalkylene glycols in the samereaction mixture or by preparing mixed polyalkylene glycol ethers. Thefirst provides a blend of separate compounds and the second providing acompound wherein R' groups in a molecule are mixed. Preferably, thepolyalkylene glycol is diethylene or dipropylene glycol and morepreferably diethylene glycol.

The oxirane compound used in the present invention can be any1,2-alkylene oxide and halo-substituted (chlorine and bromine)1,2-alkylene oxides having of from 2 to 10 carbon atoms. These can beillustrated by ethylene oxide, 1,2-propylene oxide, mixtures of ethyleneoxide and propylene oxide, 1,2-butylene oxide, epichlorohydrin,4,4,4-trichloro-1,2-butylene oxide and mixtures thereof. It is preferredto utilize ethylene oxide, propylene oxide and epichlorohydrin.

The phosphorus oxyhalide used in the present invention can berepresented by the formula: ##STR6## wherein the halogen can be the sameor mixed members of the group of chlorine or bromine. These compoundsare illustrated by phosphorus oxychloride, phosphorus oxybromide andphosphorus oxydibromidechloride. Preferably, the phosphorus oxyhalidereactant is phosphorus oxychloride.

The compositions of the present invention can be prepared by eitherbatch or continuous process.

The phosphorus oxyhalide is preferably reacted with the glycol underslight vacuum to assist in the removal of the hydrogen halide by-productthough the reaction can be conducted under atmospheric pressure orslightly elevated pressure.

The phosphorus oxyhalide and the glycol are generally reacted togetherat a temperature within the range of from -10° C. to 80° C., atemperature of from 0° C. to 30° C., being preferred.

It is essential that the phosphorus oxyhalide be reacted in a mole ratiowithin the range of from about 2.75:2 to 3.25:2 and preferably about3:2. The mole ratio is based on the total amount of glycol and oxyhalideadded. It is not essential that the total charge of each reagent beadded immediately. It is preferable that the glycol is incrementallyadded to the phosphorus oxyhalide.

The hydrogen halide evolved is preferably removed by vacuum though othermeans of purification such as sparging or the use of a refluxing inertsolvent such as hexane can be useful if desired. It is preferred thatthe hydrogen halide be removed from the intermediate reaction mixtureprior to further reaction.

The intermediate reaction mixture is reacted with an oxirane compound togive the final composition of the invention. The reaction can proceed atdecreased or elevated temperatures in the presence or absence ofcatalysts. The use of catalysts is preferred in that reaction time isdecreased and reaction temperature is lowered. Illustrative of suchcatalysts is titanium tetrachloride. Other catalysts are listed atColumn 11 of U.S. Pat. No. 3,192,242 the subject matter of which patentis hereby incorporated by reference.

It may be desirable to conduct the oxirane reaction under heat to assurecompletion of the reaction. The selection of proper operatingtemperatures is related to the nature of the reactants, catalyst usedand the quantities and can be easily determined by a skilled artisan.Temperature, within the range of 5° C. to 120° C. and preferably 30° C.to 90° C. can be employed particularly when the oxirane compound isethylene oxide.

The oxirane compound is reacted with the intermediate reaction mixtureuntil the reaction is substantially complete as determined by the amountof acid chloride remaining in the reaction mixture. This product can beused as is or further purified by known means such as distillation.

The compositions of the present invention are useful as flame retardantsfor a wide variety of natural and synthetic materials. The compositionsof the invention can be effectively used as flame retardants in amountsranging from about 0.5% by weight to about 50% and preferably from about1% to about 25% by weight depending on the particular material and itsuse.

The synthetic polymers may be either linear or cross-linked polymers,and may be in the form of sheets, coatings, foams and the like. Thepolymers can be produced by addition or condensation.

Polymers which can be effectively flame retarded by the compositions ofthe present invention can be illustrated by the polymerized vinyl andvinylidene compounds, including polymeric alkenes such as polyethylene;polymerized acrylyl and alkacrylyl compounds in the form of anhydrides,esters, nitriles and amides such as alkyl acrylates andalkylmethacrylate; epoxy resins; polyesters; polyurethanes; phenolicresins; aminoplast and the like such as specifically set forth in U.S.Pat. No. 3,976,619 at Columns 6-10, the subject matter of which ishereby incorporated by reference. The polymer is preferably urethane andmore preferably a flexible urethane foam.

Natural polymeric materials which may be flame retarded by thecompositions of the present invention include natural rubber, celluloseesters, and similar cellulose materials.

The compositions of the invention can be employed as flame retardantsfor textiles such as by incorporating the composition into the spinningdope or melt of a synthetic fiber, by thermofixation or absorption intoa synthetic textile such as polyester fabric or by incorporating theflame retardant composition into a surface finish, coating orbackcoating. Such surface finishes, coatings or backcoating willgenerally contain a polymeric binder such as a styrene-butadieneelastomer latex or an acrylic latex or a thermosetting aminoplast orphenolic resin. Similar coating techniques can be used on paper or woodincluding incorporation of the flame retardant composition of theinvention into the adhesives used for manufacturing plywood, chipboardor particle board. The compositions of the present invention can also beadded as an ingredient of the polymer such as in the reactants for theformation of a flexible urethane foam or in any other manner obvious tothe skilled artisan for applying the compositions. The method ofaddition should add on at least 0.5% by weight and preferably from about1% to about 25% by weight based on the total weight of the polymersubstrate.

The polymer formulations may also contain various conventional additivessuch as fillers, extenders, crosslinking agents, plasticizers,colorants, stabilizers and, in the case of foamable compositions blowingagents, catalysts, surfactants and the like as is well known to askilled artisan.

The present invention will be more fully illustrated in the exampleswhich follow.

EXAMPLE 1

843 grams (8 moles) of diethylene glycol was added to 1842 grams (12moles) of phosphorus oxychloride at a temperature of 3°-8° C. over aperiod to five hours. The pressure during adding was maintained at50-100 millimeters of mercury. After the addition of the glycol wascomplete, the reaction mixture was held at 3°-8° C. until the evolutionof HCl was complete as evidenced by no further weight gain in a waterfilled trap on the outlet (approximately seven hours).

To a 250 grams portion of the above reaction mixture was added 1 gram oftitanium tetrachloride and 1 gram of phosphorus trichloride. Ethyleneoxide was passed through the reaction mixture which was maintained at60°-65° C. until a sample of the mixture released less than 0.03milliequivalent of acid per gram as measured by titration with 0.1 Nalcoholic KOH. The reaction mixture was sparged with nitrogen to removeany excess ethylene oxide leaving a colorless water-insoluble liquidproduct. The product was further purified by passing the liquid througha wiped film still. The residual liquid from the still was collected asthe product having the following elemental analysis for C₁₈ H₃₆ CL₅ O₁₄P₃ :

Calculated: Cl, 23.7%; P, 12.4%. Found: Cl, 22.3%; P, 12.2%.

EXAMPLE 2

In like manner, the intermediate reaction product of Example 1 wasreacted with propylene oxide to obtain a colorless liquid product havinga viscosity of 2400 centipoises at 25° C. having the following elementalanalysis for C₂₃ H₅₁ Cl₅ O₁₄ P₃ :

Calculated: Cl, 21.6%; P, 11.32%. Found: Cl, 18.4%; P, 10.8%.

EXAMPLE 3

In like manner, the intermediate reaction product of Example 1 wasreacted with epichlorohydrin to obtain a light amber product having aviscosity of 26,000 centipoises at 25° C. having the following elementalanalysis for C₂₃ H₄₆ Cl₁₀ O₁₄ P₃ :

Calculated: Cl, 35.89%; P, 9.4%. Found: Cl, 31.6%; P, 9.9%.

EXAMPLE 4

A flexible polyurethane foam was prepared utilizing the followingcomposition:

    ______________________________________                                        Reagent               Parts by Weight                                         ______________________________________                                        Polyol (Niax 16-46, a commercial                                              polypropylene glycol manufactured                                             by Union Carbide)     100                                                     Toluene diisocyanate  51.09                                                   Product of Example 2  8.58                                                    Silicone surfactant (L-5720-                                                  Union Carbide)        1                                                       Triethylene diamine (catalyst)                                                                      0.30                                                    N-Ethylmorpholine (catalyst)                                                                        0.06                                                    Stannous octoate (50% in dioctyl                                              phthalate) (catalyst) 0.45                                                    Water                 4.0                                                     ______________________________________                                    

The toluene diisocyanate had an isocyanate index of 110. The foam had acream time of 10 seconds and a rise time of 81 seconds. The density ofthe foam was 6.3 pounds per cubic foot and the green strength was good.Green strength is a measure of the proper gelation and easily handlingcharacteristics. Poor green strength is demonstrated by a tacky topsurface on the foam and/or a foam structure which tears easily afterinitial cure.

The flexible urethane foam was tested for flame retardancy using thetest method described in Technical Information Bulletin 117, CaliforniaDepartment of Consumer Affairs, Bureau of Home Furnishings, Sacramento,California. The test basically measures the average chain length of 5specimens suspended in a burner flame. The average char length shall notexceed 6 inches and the maximum char length of any one specimen shallnot exceed 8 inches. The average afterflame shall not exceed 5 seconds.The flexible urethane foam flame retarded with the compositions of theinvention passed this test by providing an average chain length for 5specimens of 3.5 inches and an average afterflame of 0.8 seconds.

Specimens of the flexible urethane foam were subjected to an accelerateddry heat aging test. The specimens were aged in a dry oven for 22 hoursat 140° C. These specimens were then subjected to the flame retardancytest described above. The aged specimens also passed the test in thatthe average char length of the specimens was 3.9 inches and the averageafterflame was 0.8 seconds.

The above described compositions when applied by padding to 100%polyester fabric and subjected to thermofixation by heating at 210° C.to 11/2 minutes to achieve 4-5% add on, permitted the fabric to passDOC-77-3-71 (children's sleepwear flammability test). A commerciallyavailable tetrakis(chloroethyl) diphosphonate did not pass this testunder the same conditions of application.

What is claimed is:
 1. A polymer composition containing an effectiveflame retardant amount of a flame retardant composition containing asits major ingredient a compound of the formula: ##STR7## wherein Rrepresents an alkylene radical of from 2 to about 10 carbon atoms andthe halosubstituted derivatives thereof, R' represents an alkyleneradical of from 2 to 3 carbon atoms, X represents a halogen of chlorineor bromine and n represents an integer of from 1 to
 5. 2. The polymercomposition as recited in claim 1 wherein X is chlorine.
 3. The polymercomposition as recited in claim 1 wherein R represents an alkyleneradical of 2 or 3 carbon atoms and the halosubstituted derivativesthereof and R' represents alkylene radicals of 2 carbon atoms.
 4. Thepolymer composition of claim 3 wherein X is chlorine, and n is
 1. 5. Thepolymer composition as recited in claim 1 wherein said polymer isselected from the group consisting of vinyl and vinylidene polymers andcopolymers; epoxy resins; urethane polymers; polymerized acrylyl andalkacrylyl esters, amides, anhydrides and nitriles; phenolic resins,aminoplasts and polyesters.
 6. The polymer composition as recited inclaim 5 wherein said polymer is flexible urethane foam.